1. Field of the Invention
The present invention is directed, in general, to video display screens and, more specifically, to a system and method for providing a screen saver for a video display screen.
2. Description of the Related Art
With the introduction of digital versatile disk (DVD) technology and the broadcast of digital television signals, video materials that have a wide horizontal-to-vertical aspect ratio are becoming more common. Conventional television monitors have a horizontal-to-vertical aspect ratio of four-to-three (4:3). In a conventional television screen, the horizontal width of the screen is four units and the vertical height of the screen is three units.
When video materials that have a wide horizontal-to-vertical aspect ratio are displayed on a conventional four-to-three (4:3) aspect ratio television screen, typically either (1) the ends of the image are cropped to fit the central portion of the image into the 4:3 screen, or (2) the entire image is reformatted to a letterbox format that places black areas above and below the vertically-centered video image.
With the advent of high definition television (HDTV) display monitors, sixteen-to-nine (16:9) aspect ratio (widescreen) display monitors are gaining popularity with consumers. In order to display a conventional 4:3 aspect ratio television broadcast or to play video home system (VHS) tapes on these new generation widescreen monitors without distortion, the video image is typically reformatted either in xe2x80x9cpillar-boxxe2x80x9d format or is reformatted as a zoomed image. The pillar-box format horizontally centers a 4:3 aspect ratio video image on the screen and frames the video image with a vertically-aligned black rectangle to the left of the video image and a vertically-aligned black rectangle to the right of the video image. The pillar-box format allows the full 4:3 video image to be displayed without distortion.
However, both the letterbox format and the pillar-box format cause the screen to be unevenly used. That is, the video image will always be in the horizontal or vertical central portion of the screen and the black areas will always be at the edges of the screen. Continual use will eventually cause the central portion of the screen to receive a greater amount of screen burn-in than the black areas of the screen.
Screen burn-in is a phenomenon that is associated with cathode ray tubes (CRTs) of television display screens. Screen burn-in occurs when the phosphors on the internal surface of the CRT screen deteriorate over time due to the frequent presence of currents required for creating the television video image. The black areas that continually receive fewer television video images will not experience as much screen burn-in as the central area of the screen. Eventually, there will be a noticeable difference between the central area of the screen and the black edge areas of the screen due to the accumulation of more screen burn-in in the central area of the screen. Techniques to minimize screen burn-in difference, such as, moving the central video image very slowly up and down the screen during a performance or sequentially using colors other than black in the edge areas that frame the central image, have not been well received by consumers.
Consumers have also not accepted the distorted images that result when 4:3 aspect ratio video materials are forced to fit horizontally into the widescreen profile. Consumers have more readily accepted video images in which non-linear interpolation has been applied to reduce distortion in the center portion of the image. Although the process to reduce distortion with non-linear interpolation produces a more acceptable video image, the process is expensive.
The minimization of screen burn-in is even more crucial for cathode ray tube (CRT) based projection video displays because the CRT is driven harder in order to produce an adequate amount of light on the video image at the remotely located display screen. Additionally, in CRT projection video displays, there is no shadow mask to absorb energy as in the case of regular television set CRTs.
Screen burn-in differences in a display screen may also occur whenever the display screen displays a video image that does not occupy the entire area of the display screen. That is, the problem of screen burn-in differences is not limited to cases involving the display of a video image with an aspect ratio that differs from the aspect ratio of the display screen.
There is, therefore, a need in the art for an improved system and method for displaying video images in video display screens. In particular, there is a need for an improved system and method for displaying video images that do not occupy the entire area of the display screen. More particularly, there is a need for an improved system and method for displaying video images that have an aspect ratio that differs from the aspect ratio of the display screen on which they are to be displayed. Additionally, there is a need for an improved system and method for minimizing the relative level of screen burn-in in the central area of a television display screen caused by lack of comparable screen burn-in in the frequently blackened portions of the edge areas of the television display screen.
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide, for use in a video display apparatus having a display screen, such as a television, an improved system and method for displaying video images having an aspect ratio that differs from the aspect ratio of the display screen on which the video images are to be displayed.
It is also an object of the present invention to provide an improved system and method for minimizing screen burn on a display screen caused by the display of video images having an aspect ratio that differs from the aspect ratio of the display screen.
It is another object of the present invention to provide an improved system and method for minimizing the amount of relative screen burn-in that occurs in the central area of a display screen due to the lack of comparable screen burn-in in the blackened portions of the edge areas of the display screen caused by the display of video images having an aspect ratio that differs from the aspect ratio of the display screen.
It is additional object of the present invention to provide an improved system and method for minimizing screen burn-in on a display screen caused by the display of a video image that does not occupy the entire area of the display screen.
It is another object of the present invention to provide an improved system and method for minimizing the amount of relative screen burn-in that occurs in the central area of a display screen due to the lack of comparable screen burn-in in the blackened portions of the edge areas of the display screen caused by the display of a video image that does not occupy the entire area of the display screen.
The system of the present invention comprises a detection circuit that is capable of determining the aspect ratio of an active image of a received video signal. The system also comprises a video formatter that is capable of comparing the aspect ratio of the active image with the aspect ratio of a display screen, and in response to said comparison, capable of formatting the active image for display on the display screen. The system also comprises a display buffer that is capable of transferring to the display screen (1) the formatted active image and (2) a screen saver that occupies portions of the display screen that are not occupied by the formatted active image. The system also comprises a screen saver library containing a plurality of screen savers with various types of display formats.
The method of the present invention comprises the steps of determining the aspect ratio of an active image of a video signal; comparing the aspect ratio of the active image with the aspect ratio of a display screen; formatting the active image in response to the comparison of aspect ratios; providing a screen saver to be displayed with the formatted active image to occupy areas of the display screen that are not occupied by the active image; and displaying the active image and the screen saver on the display screen.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
Before undertaking the DETAILED DESCRIPTION, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms xe2x80x9cincludexe2x80x9d and xe2x80x9ccomprise,xe2x80x9d as well as derivatives thereof, mean inclusion without limitation; the term xe2x80x9cor,xe2x80x9d is inclusive, meaning and/or; the phrases xe2x80x9cassociated withxe2x80x9d and xe2x80x9cassociated therewith,xe2x80x9d as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term xe2x80x9ccontrollerxe2x80x9d means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.